03 enzymes biology notes igcse 2014

8/11/2019 03 Enzymes Biology Notes IGCSE 2014

1/16

03 Enzymes

#21 Enzymes and reactions

Many chemical reactions can be speeded up by substances called catalysts. Withinliving organisms, these reactions (metabolic reactions) are controlled by catalystscalled enzymes. Enzyme molecules are proteins.

Enzymes and reactions

Most enzyme names end inase, e.g. lipase, protease.
http://3.bp.blogspot.com/-bIShnAuC9Mo/UMBjHN_oJ0I/AAAAAAAAAzY/e6w2kPYqMCM/s1600/enzymes+3.pnghttp://1.bp.blogspot.com/-Hl1mPiUJ60A/UMBbnU7PlsI/AAAAAAAAAx8/Yt9860ARE14/s1600/enzymes+definition.pnghttp://2.bp.blogspot.com/-w7yuUx8QfBs/UMCDLXXHYrI/AAAAAAAAA2Q/c5mBm1kB6Ls/s1600/enzyme+and+reactions.gifhttp://1.bp.blogspot.com/-Hl1mPiUJ60A/UMBbnU7PlsI/AAAAAAAAAx8/Yt9860ARE14/s1600/enzymes+definition.pnghttp://1.bp.blogspot.com/-Hl1mPiUJ60A/UMBbnU7PlsI/AAAAAAAAAx8/Yt9860ARE14/s1600/enzymes+definition.png


2/16

Temperature, pH and enzymes

The activity of enzymes is affected by temperature and pH.

Effect of temperature on enzymes

The optimum(best) temperature for enzyme-controlled reactions is 37

0

C (bodytemperature).

As the temperature increases, the rate of reaction increases. Butvery hightemperatures denatureenzymes.

The graph shows the typical change in an enzyme's activity with increasingtemperature.

The enzyme activity gradually increases with temperature up to around 37C, or bodytemperature. Then, as the temperature continues torise, the rate of reaction falls

rapidly as heat energy denaturesthe enzyme. Most enzymes are denatured above500C.

Effect of pH on enzymes

The pH of a solution is how acidic or alkaline it is.

Different enzymes work best at different pH values. The optimum pH for an enzyme depends on where it normally works. It is around neutral (pH= 7) for most enzymes but there are some exceptions.
http://3.bp.blogspot.com/-dAzYF_tlz3U/UMBf2G0EDTI/AAAAAAAAAys/O9gM2YjDPuc/s1600/enzymes+2.pnghttp://4.bp.blogspot.com/-VWSrHl55N1A/UMBfiKCl33I/AAAAAAAAAyk/iKeOztDNQ4s/s1600/enzyme+and+temperature.png


3/16

Changes in pH also alter an enzymes shape and slow down its activity, but this canusually be reversedif the optimum pH is restored.

An extreme pH can denatureenzymesthe active site is deformed permanently.
http://3.bp.blogspot.com/-BoNOKPyvQPI/UMBlWJjohiI/AAAAAAAAAzg/eME72Jsg2Ok/s1600/pH+and+enzymes.jpghttp://3.bp.blogspot.com/-e5Hr61VlBqY/UMBpmbm0-XI/AAAAAAAAA0E/Rw6m7yZZKaQ/s1600/pH+and+enzymes+2.jpg


4/16

#22 Enzymes - 'Lock and key' model

Enzymes are very specific, each kind of enzyme catalyse one kind of reaction only. Tocatalyse a reaction, enzymemolecule and substrate molecule need to meetandjointtogether by a temporary bond.

Each molecule has a special shape

and an active siteinto whichitssubstratemolecule fits exactly.

This enzyme is amylase, and its active siteisjust the right size and shapefor a substratemolecule (starch in this case).

The starch slotsinto the active site.

The starch is splitinto maltosemolecules.

The enzyme is unaltered, and ready to accept another part of the starch molecule
http://4.bp.blogspot.com/-XDCZgxqi4zY/UMB_704tCmI/AAAAAAAAA1k/AuNtm9_fakc/s1600/enzyme+substrate.pnghttp://2.bp.blogspot.com/-5UFCVCWir9g/UMBy9qZAa_I/AAAAAAAAA1A/tgekIpIpojU/s1600/enzyme+3.jpghttp://1.bp.blogspot.com/-l1ykb8bNrmc/UMByKKALeUI/AAAAAAAAA0w/lzaZCdh9QAU/s1600/enzyme+2.jpghttp://3.bp.blogspot.com/-xw1X2Ibc6aY/UMByJMJO7BI/AAAAAAAAA0o/FXWIcCTxZTA/s1600/enzyme+1.jpg


5/16

# 23 Role of enzymes in germinating seeds

Seeds contain stored foodin the cotyledons to provide energy and materials

for growth. This is usually in the form of starcha large, insolublemolecule

(long chain of glucose), that keeps the food immobile. The starch needs to be

changed into a solublemolecule (sugar) with help of enzymesfor the seeds

to make use of.

In the presence of H2O, Gibberellinor gibberellic acid(GA) stimulates the

production of amylase.

Amylasebreaks down starchto maltose, allowing for the formation of ATP

(via glucose).

The energyproduced in the embryo is used to facilitate germination.

The glucoseproduced may also be used to synthesis cellulose - for cell wall

formation.

Warmthhelps speed up the process.


6/16

#24 Use of enzyme in biological washing powders

Biological washing powders contain proteaseand lipaseto remove proteinstainsand fat/grease from clothes. The enzymes break down proteins or fats on the fabric,forming water-soluble substances that can be washed away.

Example: Blood contain the red protein Haemoglobin (Hb). The Proteases in biologicalwashing powder break Hb molecules into smaller molecules, which are not colouredand which dissolve in water and can be washed away.

This makes the washing powder more effective than detergent alone, especially atlower temperatures. This save energy (no need to boil water), but if the temperature istoo high, the enzyme will be denatured.


7/16

Do it your self

Boil two standard eggs together, and push two teaspoons into the yolks so that there issome yolk left on the spoons.

Dissolve equal amounts of ordinaryand 'biological'detergents in two separate

glasses of water, and leave a yolk-stained spoon in each glass. After some time you willsee that the spoon in the ordinary detergent still has yolkon, but the yolk on the otherspoon has been digested by the 'biological' detergent. This will happen if the 'biological'detergent really containsenzymes that break down the proteins in egg yolk.

Try this

Figure above shows a box of biological washing powder.

a) Explain why:i) The presence of protease and lipase would make the washing powder moreeffective than ordinary detergent [3 marks]

ii) The powder should not be used in boiling water [2 marks]

b) Silk is a material made from protein. Explain why the biological washing powdershould not be used to wash silk clothes [2 marks]

Answer:

a) i) Protease and lipase are enzymeThey break down stains better than ordinary detergentProtease breaks down protein; lipase breaks down fat

ii) Enzymes are denatured at high temperatureb) There is protease in the biological washing powder

This would digest the protein in the silk so the clothes would get spoiled.

Benefit from using enzymes in cleaning products, toothpaste and other productsin our home.

Additional resources:

http://www.saasta.ac.za/biosciences/enzymes.html http://isbibbio.wikispaces.com/biological+washing+powders+and+enzymes
http://www.saasta.ac.za/biosciences/enzymes.htmlhttp://www.saasta.ac.za/biosciences/enzymes.htmlhttp://isbibbio.wikispaces.com/biological+washing+powders+and+enzymeshttp://isbibbio.wikispaces.com/biological+washing+powders+and+enzymeshttp://isbibbio.wikispaces.com/biological+washing+powders+and+enzymeshttp://www.saasta.ac.za/biosciences/enzymes.html


8/16

#25 Use of enzymes in the food industry

Enzymes are an integral component of modern fruit juice manufacturing and are highlysuitable for optimising processes. Fruit juices are extractedusing an enzymecalled pectinase.

Pectin is a substance which helps to stick plant cells together. Fruits like apple ororange contain a lot of pectin. The braking down of pectin makes it much easier tosqueeze juice from the fruit.

Pectinaseis widely used in order to:

increaseextraction of juice from raw material increaseprocessing efficiency(pressing, solid settling or removal) generate a final product that isclearand visually attractive

Enzymes are sometimes used when making baby foods. Proteases are used to treatsome high-protein foods, they break down proteinsto polypeptidesand aminoacidsfor young baby to absorbthe food easier.
http://2.bp.blogspot.com/-mjCd3d2lX1o/UNATDlra9pI/AAAAAAAAA9c/BeQxuEsJy-g/s1600/pectinase+fruit+juice.jpghttp://2.bp.blogspot.com/-mjCd3d2lX1o/UNATDlra9pI/AAAAAAAAA9c/BeQxuEsJy-g/s1600/pectinase+fruit+juice.jpghttp://2.bp.blogspot.com/-mjCd3d2lX1o/UNATDlra9pI/AAAAAAAAA9c/BeQxuEsJy-g/s1600/pectinase+fruit+juice.jpg


9/16

#26 Use of microorganisms and fermenter to manufacture enzymes

We obatain many enzymesfrom microorganisms. The enzymes that are used inindustry are usually obtained from microorganisms. These include bacteriaandmicroscopic fungi, such as yeast. The microorganisms are grown inside large vesselscalled fermenters.

Inside the fermenter, the microorganisms are provided with everything they needto grow and reproduce, e.g.:O2, supply of nutrients, asuitable pHand temperature.

The microorganisms make the enzymes and release them into the liquidinwhich they are growing.

The liquid can then be collected from the fermenter, and theenzymes purifiedbefore use.

Closer look at fermenter

The fermenter is a large, sterile container with a stirrer, a pipe to add feedstock*(molasses* or corn-steep liquor), and air pipes to blow air into the mixture.The microorganisms are added and the liquid is maintained around 26

0C and a pH

of 5-6.
http://3.bp.blogspot.com/-rM3ycFRwqOE/UM9VmTEuuyI/AAAAAAAAA5U/81ssd_lFHCY/s1600/fermenter.png


10/16

The enzymes produced by the microorganisms may be extracellular or intracellular:

1. Extracellularenzymes are extracted from the feedstock by filtering.2. To extract intracellularenzymes the microorganisms are filtered from the

feedstock, then crushed and washed with water. The enzymes are now insolution.

Explain words:

* Feedstock: Raw material (input) fed into a process for conversion into somethingdifferent (output).

* Molasses (syru p): Thick, dark brown, uncrystallized juice obtained from raw sugar

during the refining process.

*Corn-steep l iquor: a concentrated fluid obtained by soaking corn grains in water(containing 0,2% SO2) for 3640 hours at 4650C.


11/16

#27 Use of microorganisms to manufacture antibiotic penicillin

Three colonies of a Penicillium mold growing on an agar medium.

Antibiotics are substances which kill bacteriawithout harming human cells. They helpto cure bacterial infections. Penicillinis made by growing the fungus Penici l l iumin alarge fermenter.

Often, it is easier to use the wholemicroorganismsrather than extract its enzymesfrom it. The microorganism is grown in a fermenter, its enzymesconverta substratetoa desired product. The production of antibiotic penicillinis one example.
http://2.bp.blogspot.com/-Op5O-M1k0Ao/UM_RJ1KoizI/AAAAAAAAA58/bFYUKgxnG08/s1600/penicillinum.jpg


12/16

Fermenter

The fungus is grown in a culturemedium containing carbohydratesand amino acid.This looks like watery porridge and is stirred continuously to:

Keep the fungus in contact with fresh supplies if nutrients. Mix O2 into the culture

Roll the fungus up into little pellets(this facilitates the separatingof the liquidpart containing penicillin from the fungus lately).

For first 15-24 h, the fungus just grows. After that it begins to secret penicillin. Rate ofproduction depends on how much sugar is available:

A lot of sugar not much penicillin

No sugar no penicillin

So small amountof sugar have to be fed all the time that the fungus is producingpenicillin.

The culture is kept going until the rateof production is so slowthat is not worth waitingmore (often after a week). Then it is filtered, and the liquid is treatedto concentratethe penicillinin it.
http://4.bp.blogspot.com/-UuOCnTw-tsQ/UM_Y5olQRsI/AAAAAAAAA6s/8XkLelfkAg0/s1600/fermenter+for+penicillin.jpg


13/16

History (not included in the syllabus)

Thousands of glass fermentation vessels like this one were used in Glaxo (nowGlaxoSmithKline) laboratories to produce penicillin.

Credits: Science Museum

The penicillium mould was grown on the surface of a liquid filled with all the nutrients itneeded. This approach was replaced by the method of growing the mould within largeindustrial fermenters. The antibiotic was first used in the early 1940s and saved the livesof many soldiers during the Second World War.

Discovering of Penicillin

Sir Alexander Fleming, 1952 (photo AP)


14/16

Penicillin was discovered by chance. Alexander Fleming - the Scottish bacteriologist -accidentally left a dish of staphylococcus bacteria uncovered for a few days. Hereturned to find the dish dotted with bacterial growth, apart from one area where a patchof mould(Penicillin notatum) was growing. The mould produced a substance,named penicillin by Fleming, which inhibited bacterial growth and was later found to beeffective against a wide range of harmful bacteria.

However, it was not until World War IIthat penicillin, the first antibiotic,was finallyisolated by Howard Florey and Ernst Chain. Fleming, Florey and Chain received aNobel prize in 1945, for their discovery which revolutionised medicine and led to thedevelopment of lifesaving antibiotics.

Additional sources:Royal Society of Chemistrysciencemuseum
http://www.rsc.org/chemsoc/timeline/pages/1928.htmlhttp://www.rsc.org/chemsoc/timeline/pages/1928.htmlhttp://www.rsc.org/chemsoc/timeline/pages/1928.htmlhttp://www.sciencemuseum.org.uk/broughttolife/objects/display.aspx?id=6701http://www.sciencemuseum.org.uk/broughttolife/objects/display.aspx?id=6701http://www.sciencemuseum.org.uk/broughttolife/objects/display.aspx?id=6701http://www.rsc.org/chemsoc/timeline/pages/1928.html


15/16

#28 Summary of Enzymes

Enzymesare specialized proteinmolecules facilitating most of the

bodysmetabolic processessuch as, supplying energy, digesting foods,

purifying your blood, ridding the body of waste products. Enzymes are vital to our

health and changethe rateat which chemical reactionshappen, but without

any external energysource added or by being changed themselves.

Enzymes are proteinsthat work as biological catalysts.

Enzymes are named according to the substrateon which they

act. Proteasesact on proteins, carbohydraseson carbohydrates

and lipaseson fats (lipids). The substance that is produced by the reaction is

called the product.

An enzyme molecule has a depression called its active site, which is exactly the

right shape for the substrate to fit into. The enzyme can be thought of as a lock,

and the substrate as the key.

Reactionscatalysed by enzymes work fasterat higher temperatures, up to an

optimum that differs for different enzymes. Above the optimumtemperature,

reaction rate rapidly decreases.

At low temperatures, molecules have low kinetic energy, so collisions between

enzyme and substrate molecules are infrequent. As temperature rises they

collide more frequently, increasing reaction rate.

Abovethe optimum temperature, the vibrations within the enzyme molecule

are so great that it begins to lose its shape. The enzymeis said to

be denatured. The substrate no longer fits into the active site and

the reactionstops.
http://3.bp.blogspot.com/-SdYXc23PxZY/UNAdf4Z5hMI/AAAAAAAAA-E/AabQBRJjAP4/s1600/enzymes.jpg


16/16

Reactions catalysed by enzymes work fastest at a particular pH. The optimum

pH for most enzymes is around pH7(neutral), but some have an optimum pH

much higher or lower than this.

Extremes of pHcause enzyme molecules to losetheir shape, so they no longer

bind with their substrate.

Amylaseis found in seeds. When the seed begins to germinate, the amylase is

activated and catalyses the breakdown

of insoluble starchto solublemaltosein the seed. The maltose is used by the

growing embryo as an energysource and to make cellulosefor new cell walls.

Biological washing powderscontain enzymes, often obtained

from microorganismssuch as bacteriaor fungi. The enzymes break

down proteins or fats on the fabric, forming watersoluble substances that can be

washed away. Pectinaseis used to break down cell walls in fruits, making it easier to

extractjuicefrom them.

The antibiotic penicillinis made by cultivating the fungus Penicilliumin afermenter. The fermenter is kept at the correct pH and temperature for theenzymes of the fungus to work well.

03 enzymes biology notes igcse 2014

Documents